A pneumatic braking system may include:                first and second braking actuator means associated with the wheels of a respective axle or a respective bogie of the vehicle and to which there are connected a first electro-pneumatic control assembly and a second electro-pneumatic control assembly respectively, each comprising a charging solenoid valve and a discharging solenoid valve adapted to cause an increase and a reduction, respectively, of a pneumatic pressure supplied to the corresponding braking actuator means, and        a control unit arranged to control said electro-pneumatic control assemblies as a function of a target braking pressure, so that said assemblies cause the application of respective pressures to the corresponding braking actuator means;        said control unit being arranged to control said electro-pneumatic control assemblies so that respective braking pressure values, the sum of which at least approximately equals the value of the target braking pressure, are applied to the braking actuator means.        
In a pneumatic braking system of this type, when an increasing pneumatic braking pressure is to be applied to the braking actuators, the charging solenoid valves of the aforesaid first and second electro-pneumatic control assemblies are successively energized, in a substantially simultaneous manner, in successive instants of time separated by a predetermined interval or period, according to predetermined closed-loop pressure control algorithms, executed independently for each braking actuator means but according to common set points, so as to cause successive increases in the pressures applied to the corresponding braking actuator means.
Similarly, when the pressure to the braking actuators is to be reduced, the discharging solenoid valves of the aforesaid first and second electro-pneumatic control assemblies are successively energized, in a substantially simultaneous manner, in successive instants of time, so as to cause successive decreases in the pressures applied to the corresponding braking actuator means.
As will be more fully apparent from the following text, in a system of this type the solenoid valves of the electro-pneumatic control assemblies are energized and de-energized a large number of times, which on the one hand limits their useful service life and, on the other hand, requires more frequent maintenance work.
EP 2 527 183 A1 and GB 2 401 413 A disclose known examples of pneumatic braking systems for railway vehicles.
According to EP 2 527 183 A1 an acquisition unit acquires the necessary braking force necessary for each car of a train containing a motor car, a braking force detection unit detects an electric braking force of the entire train, a braking force adjustment unit distributes the air braking force so that fluctuations in the electric braking force are compensated by the air braking force of one car, a braking force command unit sends a command to an air brake control device depending on the command value sent by the braking force adjustment unit and the air brake control device controls the air braking of the car in accordance with the command value.
According to GB 2 401 413 A a multi axle bogie railway vehicle braking system comprises a compressed air supply which supplies, via a first supply conduit and a second supply conduit and via respective inlet and exhaust valves, respective braking actuators. The supply conduits are connected to each other through a connection passage and a connection valve, whereby each pair of inlet and exhaust valves is able to selectively control either the respective braking actuator or both the braking actuators in order to reduce the total number of valve operations.